This invention relates to an apparatus for continuously moving sheet material by spraying pickling fluid on the sheet.
FIGS. 7 and 8 schematically show an apparatus for continuously pickling a sheet in accordance with the prior art.
As shown in these figures, a tank body 11 is box-shaped with its upper surface open, and has side walls 13 installed along both sides of tank body 11 in the running direction of conveyed sheet 12 (in the right and left direction in FIG. 7)
A tank bottom 14 of this tank body 11 is so constructed that its central portion in the width direction is one-step raised throughout the length of the tank body 11 in the running direction of the sheet 12. On the raised tank bottom 14 are arranged a plurality of skids 15 for supporting the sheet 12.
In the tank body 11, waste fluid passages 16, 16 are formed at both sides of the tank bottom 14 in the running direction of the sheet 12, and fluid collecting chambers 17, 17 are formed in front of and in rear of the tank body 11.
To the fluid collecting chambers 17, 17 are attached waste fluid pipes 18, 18, which are connected to an acid fluid tank 20 which stores pickling fluid 19.
Above the tank body 11, a cover 21 is disposed to close the tank body 11. The cover 21 is connected to the upper parts of the side walls 13.
An internal cover 23 is installed to the cover 21 via a plurality of support members 24 spaced in the running direction of the sheet 12, and has side walls 22 whose ends abut on the tank bottom 14.
In the vicinity of the lengthwise center is formed an opening in each of the side walls 22 of internal cover 23. These openings serve to connect the inner part of the tank body 11 defined by the internal cover 23 to the waste fluid passages 16.
Near the lengthwise ends of internal cover 23, a first nozzle header 26 is mounted at the entrance side of the sheet 12, and second nozzle headers 27, 28 are mounted at the exit side.
Each nozzle header 26, 27, 28 has a plurality of jet holes arranged in parallel, and is connected to the acid fluid tank 20 via a supply pipe 29, so that the pickling fluid 19 can be sprayed on the sheet 12 by means of an acid pump 30 connected in the supply pipe 29.
Thus, the pickling fluid 19 sprayed from the nozzle headers 26, 27, 28 is injected into a pickling tank 31 defined by the raised tank bottom 14 of the tank body 11, the internal cover 23, and the side walls 22. The sheet 12, while running in the pickling tank 31 by being supported by skids 15, is in contact with the pickling fluid 19, so that the upper and lower surfaces of the sheet are pickled.
In this process, the pickling fluid 19 sprayed from the nozzle headers 26, 27, 28 is collected in the pickling tank 31 by the jet pressure, and then flows in the waste fluid passages 16 through the openings 25 installed in the side walls 22, being directed to the fluid collecting chambers 17.
The pickling fluid collected in the fluid collecting chambers 17 is returned to the acid fluid tank 20 through waste fluid pipes 18.
When pickling of a sheet is performed by using the above-described apparatus according to the prior art, however, a uniform jet pressure cannot be applied in the direction of the pickling tank width because a plurality of jet holes on the nozzle header 26, 27, 28 are arranged in parallel, so that the pickling tank 31 is not sufficiently and sealingly filled with the pickling fluid 19; as a result, there arises low-pressure spaces which are not filled with pickling fluid. This presents the following problems: (1) the sheet 12 floats and comes in contact with the internal cover 23, causing the internal cover to be damaged, and (2) the pickling fluid 19 is not applied sufficiently to the upper surface of the sheet 12, producing a poor pickling effect.